In view of consumer demand for four-wheel drive vehicles, many different power transfer system are currently utilized for directing motive power (“drive torque”) to all four-wheels of the vehicle. A number of current generation four-wheel drive vehicles may be characterized as including an “adaptive” power transfer system that is operable for automatically directing power to the secondary driveline, without any input from the vehicle operator, when traction is lost at the primary driveline. Typically, such adaptive torque control results from variable engagement of an electrically or hydraulically operated transfer clutch based on the operating conditions and specific vehicle dynamics detected by sensors associated with an electronic traction control system. In conventional rear-wheel drive (RWD) vehicles, the transfer clutch is typically installed in a transfer case for automatically transferring drive torque to the front driveline in response to slip in the rear driveline. Similarly, the transfer clutch can be installed in a power transfer device, such as a power take-off unit (PTU) or in-line torque coupling, when used in a front-wheel drive (FWD) vehicle for transferring drive torque to the rear driveline in response to slip in the front driveline. Such adaptively-controlled power transfer system can also be arranged to limit slip and bias the torque distribution between the front and rear drivelines by controlling variable engagement of a transfer clutch that is operably associated with a center differential installed in the transfer case or PTU.
To further enhance the traction and stability characteristics of four-wheel drive vehicles, it is also known to equip such vehicles with brake-based electronic stability control systems and/or traction distributing axle assemblies. Typically, such axle assemblies include a drive mechanism that is operable for adaptively regulating the side-to-side (i.e., left-right) torque and speed characteristics between a pair of drive wheels. In some instances, a pair of modulatable clutches are used to provide this side-to-side control, as is disclosed in U.S. Pat. Nos. 6,378,677 and 5,699,888. According to an alternative drive axle arrangement, U.S. Pat. No. 6,520,880 discloses a hydraulically-operated traction distribution assembly. In addition, alternative traction distributing drive axle assemblies are disclosed in U.S. Pat. Nos. 5,370,588 and 6,213,241.
As part of the ever increasing sophistication of adaptive power transfer systems, greater attention is currently being given to the yaw control and stability enhancement features that can be provided by such traction distributing drive axles. Accordingly, this invention is intended to address the need to provide design alternatives which improve upon the current technology.